ALSA: virtuoso: Xonar DS: fix polarity of front output

The two DACs for the front output and the surround/center/LFE/back
outputs are wired up out of phase, so when channels are duplicated,
their sound can cancel out each other and result in a weaker bass
response.  To fix this, reverse the polarity of the neutron flow to
the front output.
Reported-any-tested-by: Daniel Hill <daniel@enemyplanet.geek.nz>
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Cc: 2.6.34+ <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/oxygen/xonar_wm87x6.c

@@ -177,6 +177,7 @@ static void wm8776_registers_init(struct oxygen *chip)
 	struct xonar_wm87x6 *data = chip->model_data;
 
 	wm8776_write(chip, WM8776_RESET, 0);
+	wm8776_write(chip, WM8776_PHASESWAP, WM8776_PH_MASK);
 	wm8776_write(chip, WM8776_DACCTRL1, WM8776_DZCEN |
 		     WM8776_PL_LEFT_LEFT | WM8776_PL_RIGHT_RIGHT);
 	wm8776_write(chip, WM8776_DACMUTE, chip->dac_mute ? WM8776_DMUTE : 0);